Page 1 of 1

[SOLVED] www.google.com CNAME www.l.google.com

Posted: Mon Aug 13, 2007 8:19 am
by Chris Corbyn

Code: Select all

;; ANSWER SECTION:
www.google.com.         331524  IN      CNAME   www.l.google.com.
www.l.google.com.       214     IN      A       216.239.59.103
www.l.google.com.       214     IN      A       216.239.59.104
www.l.google.com.       214     IN      A       216.239.59.147
www.l.google.com.       214     IN      A       216.239.59.99
Does anyone know if there's a practical reason why Google have CNAME'd http://www.google.com to http://www.l.google.com before they start the round robin? I only ask because I'm about to set up another cluster of servers which will round-robin but I can't see a reason to cname like this when it works if you just directly assign IPs to the actual domain. Unless maybe they use different domain names mapping to http://www.l.google.com without the end-user thinking about it.

Posted: Sun Aug 19, 2007 4:37 pm
by Chris Corbyn
I think I realised why they've done this. I ended up coming to the same result myself. Basically if you have different domain names virtualhosted on the same hardware then you don't want to have to list all round-robin IP addresses multiple times for each domain name. It's far easier to have one domain name containing all the A records for the round-robin, then link each virtual hosted domain name to that round-robin by linking it by CNAME. Effectively it's a more maintainable way to offer redundancy :)

Posted: Sun Aug 19, 2007 4:59 pm
by Oren
I see... It's your monthly "self-discussion". Ok whatever, at least it took you just 2 posts this time. And as always, you solve the problem :wink:

Posted: Sun Aug 19, 2007 7:03 pm
by Chris Corbyn
My cries for help go unnoticed :( then I discover the answer or have a braindump and feel the need to keep the thread updated :P

Posted: Sun Aug 19, 2007 10:27 pm
by Benjamin
I get a kick out it.

Posted: Mon Aug 20, 2007 12:42 am
by timvw
I forgot to post the answer ;) (A while ago i found some forum where a guy explained it.. Also notice that the TTL of the records between google.com and x.google.com)

Posted: Mon Aug 20, 2007 4:24 am
by Chris Corbyn
timvw wrote:Also notice that the TTL of the records between google.com and x.google.com)
Ah, I don't know why I didn't pick up on that. Good point, I should change our to do it that way. I just have all our TTL's set at 200 (even though a good chunk of DNS servers won't honour TTL properly :evil: )

There's definitely no need to have a low TTL on the alias though :)